Magnetic hard disk drive systems typically include a magnetic disk, a recording head having write and read elements, a suspension arm, and an actuator arm. As the magnetic recording media is rotated, air adjacent to the disk surface moves with the disk. This allows the recording head (also referred to as a slider) to fly on an extremely thin cushion of air, generally referred to as an air bearing. When the recording head flies on the air bearing, the actuator arm swings the suspension arm to place the recording head over selected circular tracks on the rotating magnetic recording media where signal fields are written to and read by the write and read elements, respectively. The write and read elements are connected to processing circuitry that operates according to a computer program to implement write and read functions.
Recording head flying height is one of the key elements of the density of magnetic recording drives. The closer a recording head flies above the magnetic recording media, the higher density recording that can be utilized. In order to meet the increasing aerial density requirements, hard-disk drive (HDD) manufactures are seeking methods to control the fly height of read/write heads relative to the disk surface during normal operation. Such methods can dramatically improve the Bit Error Rate (BER) and drive density which are considered critical parameters in HDD systems. A closed loop and accurate control of the fly height requires an accurate estimate of the fly height.